Treatment of fabrics



Patented 3.1, 1936.

TREATMENT or ran arcs .lt'alph Brown, Bellevillc, IlL, assignm- Aluminum(Jammy. of America,

Pa.,.a corporation of Pennsylvania m1 Drawing. Application July :1, 1m,

7 Serial No. czasiv "sonimawoisi-vci I primarily by alkali dusts,liquids and gases will'be This invention relates to the protectivetreatment of fabrics to preserve them from damage and deterioration byweather, fungus growth, and gases; dusts, and liquids with which canvasand other fabrics come in. contact when exposed to the elements and whenin industrial use.

An object of the invention is to provide a fabric or cloth, such ascanvas, which W resist the action of the atmosphere in industrial areasand 10 elsewhere for a longer period than ordinary fabrics.

Another object'of my invention is to provide a fabric, and especially acotton fabric, which is esistant to the weakening effect of dampness, irand other gases, mildew and. other fungus growths, alkali dust, andalkali solutions, and to provide a method of preparing such fabric.

My invention has for further'objects such other operative advantages andresults as are found to obtain in the process and product described andclaimed herewith.

Canvas and other fabrics, especially cotton fabrics such as cotton duckand various filter cloths, are used for many purposes, both domestic andindustrial, in which they are exposed t'o-conditions whichcause adeterioration generally known and referred to as rotting. Onemanifestation of this deterioration is a loss of tensile strength in thefabric, and other changes in characteristics 7 of the fabric alsooccur.Among the factors which produce this effect in awnings, sails, tents,tarpaulins, and similar fabrics structures exposed to the elements aremoisture, mildew and other fungus growths, and certain dusts, fumes, and

85 gases which arefound in the atmosphere in some localities, as well asthe air itself. The-extent to which rotting has proceeded-isconveniently. determined by testing the tensile strength of the fabricin question and I have found that the 40 tensile strength ofuntreatedfabrics often decreases 40 per cent or; more in the course of a year'sexposure to the atmosphere.

A somewhat similar but usually more rapid deterioration takes place whenfabrics are em ployed as fllter cloths and filter bags and for otherindustrial applications, especially when they are in contact withalkalinellquids and dusts. Underv such conditions high grade canvas andother strong fabrics often rot so rapidly that they so will fall topieces when touched after an exposure ofafewhoursorless. 1 a.

' l 'orconveni'enceandbrevity, rotting inducedby .atmosphericconditionsand natural phenomena such as will be designated as fatso mospheric?deterlorationa and man: induced tion. My present and economical methodof designated "silkaline or industrial deteriorainvention provides asimple combatting' both types of deterioration, which are eliminated orat least 5 'minimized by itsapplication.

My invention'contemplates the treatment of fabrics which are to beexposed to deteriorating conditions with a c in such manner as hromiumcompoimd applied to make the treated fabric 10 highly resistant'toatmospheric and industrial conditions of an injurious nature. Inpractice, I prefer to applythe chromium compound by heating the fabricwith a solution of a trivalent ychromium salt, usually to the'boilingpoint, and 15 in some instances in the presence of a stabilizing agent.The fabric is then treated with a fixing agent, such as caustic sodasolution, which hydrolyzes the chromium salt in the fabric to 'pro-Various methods suitable reducing agen -is generally more 'duceinsoluble chromium hydroxide or hydrated 2o oxide.

of saturating the fabric with chromium salt may be used. For example,the r fabric may .be boiled or merely immersed in-a solution ofpotassium chromate or dichromate as or the like, and then treatedwithS0: or other satisfactory I' have found that it and economical.

however, to treat the fabric directly with a solusulphate or acetate.

have a concentration of abo that boiling for about 15 0 produces resultsequally as for a longer period, however,

- tion of a trivalent" chromium salt such as the The treating solutionmay ut 12.5 to 200 or more acetate per liter,

longer. I have found 86 r 20 minutes generally satisfactory as boilingand is therefore tion for use in this stepof the process dependssomewhat on theuse for which the treated fabric. L is intended.- withchromium sulphate solutions ranging inconcentration from12.5 to 200grams per liter, 1, have found that in general stronger the solution thegreater the resistance imparted-to the cloth. Withinthis range ofconcentrati -the chromium treatment has no appreciable eflect on; thefeel or cloth. when cloth so-trcated. fllteringhot alkaline solutions,

treated with the more concentrated chromium sulphate solutionsi tend tocloths intended for flexibility of the w is employed for however,fabrics 'hardensomewhat, and

preferably ll mated with solutions containing 100 grams or less ofchromium sulphate per liter.

In treating cloth orfabric in accordance with my invention, the mosteffective results are obtained if the chromium salt remains in solutionandis absorbed in the fabric as such, and is then hydro yzed in thefabric to form the insoluble chromium hydroxide. There is a tendencyto-. wards hydrolysis of the chromium sulphate when the solution isboiled, however, especially when more dilute solutions are used, andthis causes a decrease in the concentration of the solution and theamount of salt absorbed, and may lead to s of reagents. I have foundthat this difliculty can be overcome by adding to the solution a smallamount of stabilizing compound,. preferably glacial acetic acidamounting to about 4 cc. or more per liter of solution. This amount maybe varied, and with some salts such as chromium acetate the addition ofa stabilizing agent is not usually necessary.

When the fabric has been saturated with the trivalent chromium salt, itis removed from the salt solution. and treated with a fixing agent. Thisis preferably a caustic soda solution, which may suitably contain about12.5 to 100 grams of NaOH per liter. Hydrolysis of the salt absorbed inthe fabric takes place rapidly in contact with the hot (preferablyboiling) caustic, and only a few minutes of contact are required toproduce good results. When the fabric is to be employed for filteringhot alkaline liquors or for similar purposes, the fixing treatment maybe omitted, as the chromium is hydrolyzed and fixed when the fabrlcisput into use.

While many chromiumsalts and chromium compounds are effective inreducing deterioration when employed to impregnate fabrics, many ofthese are readily washed out of the fabric and consequently onlytemporarily eifective. found that substantially permanent normallyproduce rotting is imparted to fabrics which. are properly impregnatedwith insoluble chromium hydroxid and that this is most convenientlyeffected by saturating the fabric with a salt of trivalent chromium thesalt in situ, as described Example 1 hereinabove.

direction of the cor; were boiled for periods f ranging from 7.5 minutesto 60 minutes in caustic soda solutions 12.5 'to 100 grams of NaOH perliter. These test strips were exposed to the atmosphere for a year,along with untreated strips. At the end of the year the strips weretested, and the-strengths of the fourstrlps in each set were averaged.The average strength of the untreated strips was 114 pounds per inch;strips boiled in solution containing 50 grams of chromium sulphate perliter and then boiled 30 7 minutes in caustic soda solution containing12.5 grams per liter averaged 158 pounds per inch; and strips boiledwith a 200 gram per liter chromium sulphate solution and thenwith a 25gram.

I have 7 v resistance to 'both atmospheric and alkaline conditions whichn hydro hs 1 rotting,which lites-,0! glacial acetic acid,

per liter caustic. soda solution for 7.5 minutes averaged 189 poimds perinch.

Example 2 A set of four test strips of filter cloth .was boiled in achromium sulphate solution containing 100 grams per liter ofCI2(SO4)3.15H2O for minutes. This set and a similar set of strips ofuntreated cloth were then subjected to an acceler- Example 3 A set oftest strips of filter cloth was boiled in a solution containing 50 gramsof chromium acetate per liter for 15 minutes, and then subjected to anaccelerated rotting test as in Example 2, along with a set of untreatedcloths. After-the test the average strength of the treated cloths was172 pounds per inch, while the average strength of the untreated stripswas 16 pounds per inch.

Various examples have been given hereinabove in order that the operationand application of my invention may be more readily comprehended, but itis to be understood that these examples are given by way of illustrationonly, and not as limitations, and that my invention may be variouslyembodied within the scope of the appended claims.

I claim as my invention:

t to

1. In a process of rendering fabric rotting, the step comprising boilingfabric with a solution of chromium sulphate containing about 4cc.otglacialaceticacidperliter.

2. In a process of rendering fabric resistant to rotting, the stepcomprising boiling fabric with a solution containing from about 12.5 to.about 200 grams of vCn(8O4):.15H:0 per liter and a small amount, notless than about 4 cc per liter, of glacial acetic acid.

3. 'Iheprocessofrenderingfabrlc resistantto boiling the fabric with asolution 'of chromium sulphate stabilized with acetic acid, and thencontacting the fabric witha hot alkaline solution.

4. The pmccm of rendering fabric resistant to rotting, which comprisesboiling the fabric for an hour or less with a solution containing about12.5 to200gramsofchromiumsulphateandabout4 cc. of glacial acetic acidper liter, removing the fabric from the solution, and boiling the fabricwith a solution containing caustic soda.

5.1naprocessofrenderingiabricresistantto rotting. the step comprisingimpregnating fabric with a solution containing from about 12.5 to about200 grams of Cr2(SO4):.15HsO per liter andasmallammmt,notlessthanabout4cc.per

6. The process of rendering fabric: t no ,whichim-- ric wiih a solutionof chromium sulphate stahiliaed with acetic acid, and thencontacting'the faln'icwithahotalkalinesolution. I. The process-drendering nlter cloth redanttorotflng,whichcomprises aclothwithasolution containin' gabout f12.5to

after filtering a hot alkaline solution through the cloth. whereby thechromium sulphate gis hydrolyzed and an insoluble chromium hydrii clothwith a solution containing about 12.5 to 100' grams of chromium sulphateand about 4 cc. of

glacial acetic acid per liter and thereafter filtering a hot alkalinesolution through the cloth whereby the chromium sulphate is hydrolyzedand an insoluble chromium hydroxide is formed in the 5 cloth.

RALPH W. BROWN.

